Hi guys, first post here. Just bought a GS500F today and when I took it for a spin the bike feels like it hits a brick wall at 5000 rpm. Just loses all acceleration until i kick it up to the next gear and then does the same when i hit 5000 rpm in that gear. What the hell is going on!!!!!! Cheers guys.
Probably jets clogged. Lots of people complain about that. Do a carb cleaning
The carbs have just been cleaned out before i bought the bike
Unless the PO is a very good friend / family member, don't believe them. Some people will say anything to sell a motorcycle.
What exactly is it doing after 5k rpm? Is the engine revving higher (to 6k rpm+) and the speed of the bike not increasing to match? Or will it not rev past 5k under load?
... will it rev past 5k in neutral if you raise the throttle steadily or just bang it on?
If you can't get it past 5k rpm in final gear, being stuck driving at 55mph, but can get it to run faster in 4th gear, it might be the main jet clogged.
Could be a handful of things, none of which are the jets. Jets are throttle position dependent. If you can go WOT through the gears and then the engine starts bogging down it's likely not your carbs.
- Choke could be stuck on
- Low oil
- Oil is too viscous
- Broken ignition advancer/Bad timing
Perhaps you can add some detail as to what is happening? Are you able to get it past 5k rpm and it just bogs there for a bit? Or does it stall at 5k? Is it completely limited at 5k in all gears? Are you able to open the throttle all the way in any gears? At face value it does sound like a clogged main or mid-main jet.
And as Rich said, don't believe that the carbs were cleaned unless it is someone close to you. People will say anything to sell a bike and beyond that, some believe that spraying carb cleaning in the fuel intake valve is equivalent to a cleaning.
If the plugs are very close to white, indicating running too lean, then I would suspect the jets, particularly the mains, and the orfice at the bottom of the main emulsion tube which surrounds the needle controlled by the air slide. I would also make sure the emulsion tuble orfices are cleaned, preferably mechanically and inspected optically.
regards
mech
+1 on the carb clean.
Also check out the air filter. Last summer I got a Hi-flo stock replacement and it actually choked the bike up enough that it wouldnt pull past 6,000 rpm at wide open throttle. It was an HFA-3503.
I contacted Hi-flo and they sent me a replacement made for an older gsx750 or something like that. looked similar to the other one but must have been able to displace more air. It works well!
Here is the email from HIFLO:
Scott,
We are aware that the GS500 can be very touchy with differences in fuel/air mixture but as yet have not found a way to pinpoint how to determine which bikes are most likely to be affected...for the vast majority the 3503 works as it should.
There is an alternative. I would be happy to send you a 3604 for to try on your bike (just let me know how it works for you and the VIN from your bike so we can add it to our list of bikes that prefer the 3604).
If you are interested in trying the alternate filter, please send me your address so I can get it out to you.
Regards,
If the bike hits 5k then revs really high with no acceleration, you probably need to do a three point clutch adjustment
The issue was a filthy air filter and a bit of crap in the carbs. The bikes only covered 4,500 miles but the filter hadn't been changed in 10 years.
Thought id give you guys some closure haha.
Thanks.
My 71 Honda CB350 ran fine on the original 40 year old air filters after I thoroughly cleaned the carbs, in particular the main jets and emulsion tubes. It sat for 28 years. It had 4718 miles when I bought it.
An air filter has to get pretty clogged up to affect performance. I'd bet unless the air filter was black it was mostly the jets.
regards
mech